Effect of Nitrogen and Phosphorus Management on Growth and Yield of Foxtail Millet [Setaria italica L.] During Summer Season in Odisha, India

India is the largest producer of many kinds of millets (foxtail millet, finger millet, barnyard millet etc.), which are often referred to as coarse cereals.  Foxtail millet is consumed by the rural / tribal population of warmer region in India (Andhra Pradesh, Odisha, Karnataka, Tamil Nadu, Uttar Pradesh and Southern Rajasthan). In India, small millets occupied an area of 64990 ha with a production of 39990 t and the productivity of 602 kg ha^-1 during 2017-2018 (AICRP, 2017-18). According to the annual progress report (2017-2018) of AICRP on Small millets,the cultivated area in Odisha is 25400 ha with a production and productivity of 12700 t and 501 kg ha^-1 respectively. In India, the yield potential of foxtail millet is low as compared to the potentially achievable yield because of inadequate application of fertilizers, conventional cultivation of low yielding cultivars and lack of good management practices. Maximum yield potential can be obtained by growing high yielding varieties having tolerance to drought, pests and diseases and response to fertilizer application (Choudhary et al., 2013: Rahi and Choudhary, 2016).Recent studies have shown that newly developed varieties of foxtail millet are more responsive to nitrogenous fertilizers (AICSMIP, 2017). Intensive agriculture demands full exploitation of the varieties with available resources, mainly fertilizers while being economic at the same time (Rahi and Choudhary, 2014, 2016). Nitrogen is considered to be an important nutrient for growth and development of plants. It plays an important role in building units of proteins in the plant system (Choudhary and Suri, 2009). Thus, N nutrition not only influence productivity but also quality (Choudhary and Rahi, 2018). Beside N, phosphorus is of paramount importance for increasing yield. Phosphorus play an important role in energy transfer in the living cells by means of high-energy phosphate bonds of ATP (Bai et al., 2017). Phosphorus deficit is the most important restrictive factor in plant growth because it promotes root development that in turn enhances uptake of other essential elements (Kumar et al., 2016). The experiment was taken up during summer as the farmers in some areas in southern Odisha usually take rice during kharif season followed by short duration green gram (Nov-Jan) in some areas and major area is kept fallow. The crop water requirement of foxtail millet is less which is suitable to grow in summer season. Where overwater is available during summer and is sufficient for few number of irrigations, this crop can fit in to the cropping system. Keeping these points in view, an experiment was conducted to test the performance of foxtail millet at different levels of nitrogen and phosphorus during summer.

The field experiment was carried out during the summer of 2018 (Feb- May) at Bagusala Research Farm, Department of Agronomy, M.S.Swaminathan School of Agriculture, Centurion University of Technology and Management, Paralakhemundi, Odisha on sandy loam soil having pH of 6.5 and low in available nitrogen (144 kg/ha^-1) and high in available phosphorous (423 kg/ha^-1) and available potassium (896 kg/ha^-1) and medium in organic carbon content (0.50%). The experiment was conducted in a split plot design. The main and sub plot treatments consisted of nitrogen and phosphorous levels respectively. The treatments were four N levels (0, 20, 40 and 60 kg N ha^-1) and three P₂0₅ levels (0, 20 and 40 kg P₂O₅ ha^-1). Common dose of 30 kg potassium was applied uniformly to all the treatments along with P₂O₅ as per treatments at sowing. Nitrogen was applied in two splits, 50% at sowing and remaining 50% at 25 days after sowing (DAS). Foxtail millet crop variety SIA-3156 was sown on 23^rd February 2018 at a spacing of 25 cm x 10 cm. Harvesting was done on 21^st May 2018. The basal dose of fertilizer was applied in the furrow and then seed were sown at a spacing of 10 cm with in row and covered with soil. Total of 6 irrigations were given during the entire growth period. The rainfall received during the crop growth period was 12.7 cm. Pendimethalin was applied on 3^rd day after sowing to control weeds. Observations on growth, yield and yield attributes were recorded and subjected to statistical analysis using standard procedures (Rana et al., 2014).

Growth and yield attributes
 
There was significant increase in plant height and number of leaves of foxtail millet with increase in application of N levels but it was not significant due to P levels (Table 1). Highest plant height and number of leaves per plant was observed with nitrogen application of 60 kg ha^-1.
 

       
The number of earheads per m^-2, ear head length, grain weight per earhead and 1000 grain weight differed significantly due to nitrogen levels. However, it was not significant due to phosphorus levels and interaction of nitrogen and phosphorus levels (Table 2). The number of earheads and ear head length was significantly higher with application of 60 kg N ha^-1 as compared to 0, 20 and 40 kg N ha^-1. The difference in earhead length between 40 and 60 kg N ha^-1 was not significant. The grain weight panicle^-1 increased significantly with increase in nitrogen levels from 0 to 40 and grain weight in these treatments was significantly lower than that of 60 kg ha^-1. On the other hand, it did not differ significantly between 20 and 40 kg N ha^-1. The 1000 grain weight was significantly higher with application of 60 kg N ha^-1 as compared to other levels of nitrogen application.
 

 
Yield
 
The dry matter at harvest, grain and straw yield was significantly influenced due to nitrogen levels and it did not differ significantly with application phosphorus and interaction of nitrogen and phosphorus levels (Table 2). The dry matter at harvest was significantly higher with application of 60 kg N ha^-1 (3823 kg ha^-1) over that of 40 kg N ha^-1 (3075 kg ha^-1) and 20 kg N ha^-1 (3110 kg ha^-1). The dry matter production in latter two levels of N was comparable with each other and significantly superior over 0 N ha^-1. The dry matter at harvest increased with increase in P₂O₅ level from 0 to 20 and 40 kg ha^-1. The grain (1546 kgha^-1) and straw yield (2277 kg ha^-1) was significantly higher with application of 60 kg N ha^-1 over that of 0, 20 and 40 kg N ha^-1. The grain yield and straw yield observed with 20 (1152 and 1958 kg ha^-1) and 40 kg N ha^-1 (1144 kg ha^-1 and 1931 kg ha^-1) was comparable with each other and significantly higher than that of 0 kg N ha^-1 (686 and 986 kg ha^-1). Straw yield in latter two levels of N was comparable with each other and significantly superior over that of no nitrogen application.    
 
Economics
 
Cost of cultivation was maximum with 60 kg N + 40 kg P₂O₅ ha^-1 (Rs.19982 ha^-1) followed by 60 kg N + 20 kg P₂O₅ ha^-1  (Rs.19830 ha^-1) and 40 kg N + 40 kg P₂O₅ ha^-1 (Rs.19772 ha^-1) (Table 3). The minimum cost of cultivation was recorded in 0 kg N and 0 kg P₂O₅ ha^-1(Rs.19258 ha^-1). However, the cost of cultivation increased gradually with increment of nitrogen and phosphorus levels. Maximum gross and net returns and B: C ratio were recorded with application of 60 kg N and 20 kg P₂O₅ ha^-1 (Rs.37617 ha^-1, Rs.17781 ha^-1 and 1. 90). This was due to high grain and straw yield of foxtail millet in this treatment as compared to other treatments. Minimum gross and net returns were recorded with 0 kg N and 0 kg P₂O₅ ha^-1. The net returns were negative where no nitrogen was applied.
 

 
 Nitrogen levels
 
Grain yield differed significantly due to nitrogen levels and significantly higher with application of 60 kg N ha^-1 over 0, 20 and 40 kg N ha^-1 with respective improvement 125, 34 and 34% respectively. The increase in yield of the crop is a function of yield attributes which are complementary dependent on vegetative growth and reproductive stage. The dry matter at harvest was significantly higher with 60 kg N ha^-1 over that of lower levels of N (Table 2). The significant improvement in drymatter, yield attributes like number of earheads, earhead length, number of grains per earhead, grain weight per earhead and 1000 grain weight with application of 60 kg N ha^-1 over that of 0, 20 and 40 kg N ha^-1 ultimately helped in increase of yield in the former level of N application. The positive response of yield components of foxtail millet to fertilizer application could be ascribed due to improvement in growth of the crop as evident from increased dry matter accumulation (Paul et al., 2016). This suggests growth availability of nutrients for growth and development of reproductive structure ultimately realizes higher productivity (Choudhary et al., 2010). The increased availability of nutrients and photosynthesis might have enhanced the yield attributes (Table 2) and there by grain yield (Paul et al., 2016). The biological yield and dry matter production is important for determination of grain yield (Donald, 1962). The grain yield observed with 20 and 40 kg N ha^-1 was comparable with each other and significantly superior over 0 kg N ha^-1. The application of N helped the crop to produce higher level of growth and yield attributes in 20 and 40 kg N ha^-1 over 0 kg N ha^-1. It has been observed that the grain yield  had positive co-relation with growth and yield attributes (Bai et al., 2017) indicating  improvement  in these parameters has increased the yield with application of 20 and 40 kg N ha^-1 over 0 level of N. It has been reported that increase in added nitrogen improves the nitrogen uptake (Dhillon et al., 2018). Further, it was significantly greater at higher levels when compared to lower levels (Jyothi et al., 2016). The availability of higher levels of nitrogen to the crop might have helped in greater uptake and there by drymatter production and yield attributes in increased levels of N application, hence the yield (Choudhary et al., 2008). Such improvement in yield was reported in foxtail millet with increased levels of N application (Jyothi et al., 2016).
 
Phosphorus levels
 
The grain yield did not differ significantly among P₂O₅ levels 0, 20 and 40 kg ha^-1. The foxtail millet crop was grown after kharif rice and the land is under one year crop rotation of rice –rice for several years .The rice crop is fertilized with chemical fertilizers NPK. The experimental plot where foxtail millet was grown is having low nitrogen and high phosphorus. As the fertility status of the soil is high, thus crop did not respond to added phosphorus. Further, it was observed that there was no improvement in growth and yield attributes (Table 2). It has been mentioned earlier that there was positive corelation between grain yield and yield attributes (Table 2). As the yield attributes like number of earheads per unit area, grain weight per earhead and earhead length did not improve due to application of phosphorus, the grain yield increase with phosphorus levels was not observed. Similar results of non-responsiveness of foxtail millet to phosphorus application were reported by Kalaghatagi (2000).
 
Economics
 
Net returns were higher at 60 kg N ha^-1 with 0, 20 and 40 kg P₂O₅ ha^-1 application as compared to 0, 20 and 40 kg N ha^-1 at all three levels of phosphorus. Maximum gross and net returns were observed with application of 60 kg N and 20 kg P₂O₅ ha^-1. It is interesting to note that at 0 level of N with 0, 20 and 40 kg P₂O₅ ha^-1, the net returns were negative. However, the loss decreased with increase in P₂O₅ levels. Further the B:C ratio at 0 kg N ha^-1  with different levels of  P₂O₅  was < 1.0 and the B:C ratio increased with increase in N from 20 to 40 and 60 kg N ha^-1.

It can be concluded that during summer under irrigated conditions, application of 60 kg N ha^-1 and 20 kg P₂O₅ ha^-1 to foxtail millet results in higher yield and net returns in Southern Odisha.